docs: add doc comments to ISession members

src/DBus.Services.Secrets/Sessions/ISession.cs

@@ -12,7 +12,18 @@ public interface ISession
     /// </summary>
     ObjectPath SessionPath { get; }
 
+    /// <summary>
+    /// Formats the provided data into a <see cref="Secret"/>, which may involve encrypting it with the session's data.
+    /// </summary>
+    /// <param name="data">The data to format as a secret.</param>
+    /// <param name="contentType">The content type of the data.</param>
+    /// <returns>The formatted <see cref="Secret"/>.</returns>
     Secret FormatSecret(byte[] data, string contentType);
 
+    /// <summary>
+    /// Decrypts the provided secret using the session's data.
+    /// </summary>
+    /// <param name="secret">The secret with the data to decrypt.</param>
+    /// <returns>The decrypted secret.</returns>
     byte[] DecryptSecret(ref Secret secret);
 }